Papa Tom, I think your problem is that you want to make this purchase only once. Since you are an overthinker, as I am, you're going to have to do a few iterations. Start with something moderately priced, not cheap, not outlandishly expensive. You might be satisfied. Then you might be able to refine or modify it. Or replace it entirely. If you have more than one bike, that's not such a bad thing. Learning is worth some money, anyway.

I use battery lights on some of my (too many) bikes and dynamos on two so far. I'm collecting dynamos and will be putting them on other bikes, including one or two of my wife's. You've learned about the stress of not knowing when your battery will crap out.

One way to get the best of both worlds is to use both types at once. I sometimes use a battery light and a dynamo light, just because I can, or because I want to be extra cautious.

Some of those proprietary battery packs have 18650 cells in them. These cells are still a little odd but they're available individually, and you can get chargers for them. I happen to like flashlights that use this type of cell. In fact, I believe many laptop computer battery packs have these cells in them.